Magnetic escapement



" p 1965 KAZUO ISHIKAWA ETAI. 3, 08,287

MAGNETIC ESCAPEMENT Filed 001:. 12, 1962 s Sheets-Sheet 1 p 3 965 'KAzuoISHIKAWA E 3,208,287

MAGNETIC ESOAPEMEN'I' Filed om. 12. 1962 a shes 154mm. 2

MAGNETIC ESCAPEMENT Kazuo Ishikawa, Tokyo, and Koichi Iwaki, Gyoda-shi,

Saita'ma-ken, Japan, assignors to Jeco Company, Lim

ited, Tokyo, Japan, a corporation of Japan Filed Oct. 12,1962, SenNo.230,182

Claims priority, application Japan, Oct. 21, 1961, 36/52 .154; Oct. 26,1961, 36/38,4l0

' 8-Claims. (Cl. 741.5)

This invention relates to improvements in a magnetic escapementmechanism.

The magnetic escapement mechanism is already known, for example, duetoBritish Patents Nos. 660,581 and 838,430. In a magnetic escapementmechanism, a permanent magnet is secured to theforward'end of aresilient material fixed at the other end to a supporter to form anoscillator oscillating around the fixing point of the J resilientmaterial as a fulcrum, and the undulating magin case days are, plottedon the abscissa and rates are plotted on the ordinate to show thecharacteristics of the magnetic escapement, as represented by the curveA, the rates (time keeping) will vary every day with the lapse of timeand will gradually become higher as a whole. The fluctuation means thefluctuation of the daily rates as represented by D on the curve A in;FIGURE 10.

The reason why the magnetic-escapement mechanisms previously proposedhave the defects known as speeding up and fluctuation is considered tobe that the rela-- tive difference between the oscillating energy keptby the oscillator used andthe energy given and received by magneticattraction between the magnetic poles of the magnet, an element of theoscillator, and the undulating magnetic track of the escape wheel is notlarge enough and that therefore the oscillatory motion of the oscillatorwill be soigreatly disturbed by the torque fluctuation appearing .on theescape wheel or. the like that, the oscillating frequency will be biasedand the speeding up" and fluctuation" will be caused- Thus, if therelativev difference between both energies is made large, such defectswill be able to be eliminated. However, in theuse of the conventionalBalance Reed" as the oscillator, its sharpness of resonance is so lowthat the relative difference between both energies has not been able tobe made large. Such sharpness of resonance corresponds to thecharacteristics of a resonant circuit in an electric circuit.

.The above mentioned sharpness of resonance is represented by the curveA-in FIGURE 11 in which the abscissa represents the frequency n of thedriving force and the-ordinate represents the oscillators amplitude Y.

In the conventional magnetic escapement mechanism using a Balanced Reed,of a low sharpness of-resonance (thevalue of Q about 100 to 200), theoscillatingenergy of the Balanced Reed leaking from the supporting partof the"Balance Reed is so large that the ground plate to which thesupporting part of the Balance Reed is attached, the supporting part andall the members in 'contact with the ground plate will integrally forman oscillation system. Therefore, the frequency, of the Balance Reedwill not be determined by only the physical conditions of the BalanceReed itselfas, for example, the: I Youngsmodulus of the resiliency oftheBalance Reed" and the mass of the magnet, but will also be influencedUnited States Patent by the physical conditions of all the membersforming the oscillation system. i The present invention has been made toeliminate the above mentioned defects and is to suggest using a tuningfork instead of the conventional BalanceReedT in amag netic escapement.I v;- A main object of the present invention is to'provide' a magneticescapement mechanism which is very high in precision by synchronizing anescape wheel with the stable Y oscillatory motion of a tuning fork.

The present invention shall now be explained with ref.- erence to theaccompanying drawings.

FIGURE 1 is a perspective view of an embodimento I the magneticescapement mechanism of the present invention. I

FIGURE 2 is a plan view of another embodiment of the magnetic escapementmechanism.

FIGURE 3 is a side'view of the same.

FIGURE. 4 is a plan view of a still another embodiment wherein a magnetis set betweentwo escape wheels with which a tuning fork is magneticallycombined.

FIGURE 5 is a side view of the same.

FIGURES 6 and 7 are perspective views of otherr spective embodiments ofthe tuning fork.

FIGURES 8 and 9 are explanatory views showing the oscillating states ofthe tuning fork.

FIGURE 10 is a graph comparatively showing the speeding up andfluctuation of a conventional magnetic escapement mechanism and those ofthe magnetic escapement mechanism according to the present invention.

FIGURE 11 is a graph showing the relation between the sharpness ofresonance and thefrequency bias of the Balance Reed and the tuning fork.

In FIGURE 1, 1, 2 and 3 are ground plates. 4, 5, 6 and 7 are pillars tofix the said ground plate. 8 is ,a direct current motor.

9 is a rotary shaft for the said. motor. 10 is a spring I attached tothe said rotary shaft. 11 is a rotary disk. 12 is a pin attached to thesaid rotary disk and engaged with thefree end of the spring 10. 13 is ashaft for the rotary rality of corresponding elongated apertures 25balinedwith the projections 25a so as to form the conventional undulatingmagnetic track. 28 is a gear fixed to'a shaft 27. 29 is a tuning fork.35 is a pillar-to fix the tuningfork 29 to a supporter 30 fixed to theground plate l-with screws 31. 32 and 33 are magnets secured as opposedto each other to both forked ends of the tuning fork. The

said magnets are in the form of rings or frames cut in one place ofthemagnetic circuit to have magnetic ,poles in the form like a slit. Theescape wheel 25 is interposed between the Nxand S poles of one 32 of thesaid magnets. In this case, the other magnet 33 not combined with anundulating part of the escape wheel 25 can bereplaced with any otherweight that can be a counterweight for the magnet 32. a

The operation of the magnetic escapement mechanism of'the presentinvention shall now be explained. The rotation of the direct currentmotor 8 .will'be transmitted to the rotary disk 11 through the spring 10as a shock I absorber and then to the escape wheel 25 through the gears14, 15, 17, 18, 21, 22 and 24. The escape wheel is so provided as torotate with the undulating magnetic track interposed between the N and Spoles of the magnet 32 secured to the forked end of the tuning fork, and

I istherefore magnetically an oscillatorinuthe -presentinventionismuchlgreater than' the;.- sharpness of: resonanceaioffa conventionaloscillator" Qof the tuning; fork heing about 10005 t;250'0;-. (Sbeathecurvve 'Bain FlGURE.1=1i)" i magnetic devices; the frequency bias will]be. An.

} endsof the tuning fork 29 fso thatboth: magnetically combinin'g"points may be' symmetrical with; re'spectatowthe: centeroftheescapet'wheeli p In; case-:onlythemagnet;32i securedf tothez forked endamechanical 'oscillatingmlement', theret willi-be caused such of a:cantilever; having: the: suppotting gpointr34 0f? 31f combined; withthemagnet 32'? and; rotates at a: constant speed. as in: auknown: magneticescapement device; Thist-constant 'rotationl williibez. transmitted; tothe shaft -27Tthrough the:gears 19'-an(1" 28". A

- The sharpn'essaof resonancesofthettuningz-n-fork used as employing? aBalance R'ee'dJ." for example, the value of:

FIGURE 11 shows the'csh'arpness of resonance of the Balance. R'eedjused* in -a' conventional magnetic escapement mechanismqand, that ofthe'rtuninglforlc. in. the present; invention.-as-.- driven'vbythe.same;v magnitude; of; force; The curve Althereir'i.ire -n'esentst the:sharpness ofs' resonance of? the: conventional: magnetic escapementmechanism: and theucurve.B represents "that of the'present ir'iventiomvIn- FIGURE 11; the ordinate epresents the. amplitude and; the: abscissalrepresents the frequency of the driving force. If, ins order; tosynchronizeythates caperw-heel, eachaofi'the; two" type oscillators:discharges the: same-amount: of the oscillating energy kept; byit; and

its amplitude-is reduceds' to: Y',';e the:;: natural. frequency? of tthe conventional oscillaton-willlf. be." biased from" n5 to: n +A'n" bit125,. ';Ari'. That is totsay; in: case." theos'cillator" brakes th'eiaclvan'ciiig:v escape; wheel the: frequency bias? will be: An 1 0n 1then contrary, in casewtheg escapeiwlieel is to be rotated by;the-oscillator; driven.- by- 's'ome'; electro Howeveni the frequencybias offithe' tuningriforkt will be An which. is smaller thanittherfrequency 'biasi'iAnfi" of theconventional-{Balance:Reedi?"Thenefore-,:theeflhctuationof-the-rates willbbesmalleim In FIGURE" 1only. theurriagnetrl32fl o'flthe" magnets 32'. landi 33' secured. to theforked'iendsz' of the tuning i for-1629"" 3 is magncticallycombinedtwitli the-vescape-Hwheeli How-- ever; thechara'cteristicsscanbe fur'thenximprovedrby; mag netically combining; both magnetsv 32 Cand: 33with' the;-:

' escape wheeli25. Only thecoupledi partfofl thettuningr forkandiescaperwheel isrillus'ti'atedl in FIGURES-2522mm 3 L .t

' However, 1 as' shown in the: drawings; the escape wheel 25" isrotatahly inserted between: the respective NZandS' poles of theumagnets32Land' 33' securedito bothforkci'.

of the-ftunihgxfork, ismagnetically combined" with: the: 1681" capewheel-25 215 shown: in: FIGURE 1", the tuningn fork, willoscillate-1aroundiitslsupportipg pointgii i? as:a;fiilct'urntlv In: suchcase,v the oscillatorwillflform: a; kindoff a: canti," lever..Therefore,inrucase theituningforkt is use'di'as suchi motion" which 'isnotl the nornialioscillatory; motionlcofi the? tuning: fork as, is"shown in: FIGURE"! 9; that is; to; say; such complicated? oscillatorymotion": as results from; a

combination of the; oscillatory motion 1 of "the: fin 29 tuningitfork" 29"as a fulcrum; and: the: normal oscillatory motion: of; theituningfork'29 as-, :isshown' in: FIGURE-9 8: Consequently; thesafety of-Jithe:operation willrbec impaired: ina some cases. This'defectihasabeen:eliininatedirby such z f'orr'nationa asri'sras'hown'in FIGURES"21' and; 3;: fiTlie: escape wheel 2.5?is. so provided as to bevfr'eelyrotatable between the: pols:,N' and Si and'l-N andaS'g; ofi the magnets321andk33; respectively; Thetuning, forlc and theaescapefwheelaremagneticall'y combined with: each other" by magnetic-fluxes.hetweenrth'e: magnetic poles N1;- and'S' and? N andasin. Therefore;tuningzfork 29 as the oscillating; element and:- their escape wheels 25will 1 70:v be: combined witheach othee ajt two points P and- P5;(seefFIGUKESiZKandBE) Therefore;- the forces received? by themagn'ets32: and 33 ftom thezescapezwheclz' willTso' act asto: make-the tuning:fork produce: a .norm'al oscilla tion'andlto alwayscanceheachqothcr.Thus-.th'e. force l5;

manages? tuning: fork 29 10 the. body of? a: cloelc or th 1 likevis: so3 inuchr smaller: than ther energy leaking in: the. conventional imagnetic escapementr de ice using: the Balance Real?"conventional'producti andi LB tion" withith receivedlby the.rotary-shaft ifiiwilli also" and thef wear. of the: shaft can" bepreventedi Furthena: lating energyleaking; from tlJCiSIIPQOItiHg-JPOloscillatofl-that' there willi hegsuhstantially no variatiomofi:

the frequency by, the infliiencexofthei loosening-01 thelikeE- of anypart; of tl1e= body-"ofi' the': clock: with the.-lapse:= of

tir'nei Therefore;fspeedingzupi 'andi=fluctuation?"cambe solved without"the i' eed'i"ofsfenlargings thef mass f of'the: sup:- 1

portin'g pillar:305=iniorderrto'tmakezthei xnechanicalaimped ance: of Ithe" supporting: portion 1 infihite'ly large. is: evident: from:experiments andf. canetbe easily "understoodi by: comparing; the:variationsoi' 'thearates' o f ment' mechanisms: represented" by theycurvA? enterinvention?v lII'S FIGURE I O'I.

Further; by makingrthea'fhrked 'endsaofithe tuningifdrkaFIGURESMEa'hiTKL thevma-gnetic comhina:-; fez

as'showmim errescape rwheel'ican he improvediw Also the structureishown"FIGUREflf'iseadopted;it wi a easy totsoetermihexthe requency at any-'desired value :by-

properly" selecting? the;- dimensionsa of" contact pit'ecesgi llI?" landmtl I p Y SincethezQTofi:the:tuningggfrhtemplbyedi ih1the =presentinvention i'sx: muche; higher: the v th the. driving: energya required?to oscill'aterthe" tuning fork at: any :iglesirediiamplitude may be.relatively small? In" order.- tofim'aintainctheoscillation; onl'ya:loadenergys'ancli: los'sirenergy need? fedto;' the: device; In:the-"convene tiona'lrt iniepiecez mechanism 'ofthisrkind; the-lossenergy;

occupies: the: greatenpartf. ofi'th'e: fedi energy,v but when the 1tuningst'orkiszusedziiraccordancewiththisinvention;such V v lossxenergy" is:considerably: smallei' than in ithe 'conven ti'onal. balancesreed i devices; E'orfthe; above mentionedhreasons; even: if alimagneticzconnectingmeansiwhichisnot soxpowerful as' a. mecha cal" connecting;means: isiusedi for the? connection" of?" th'e.-:

fiihtuningforksuch; as a; fork: having; a: high -fi"equency-' 05100 400cycles;.pervsecond;-for' example, may; still f be: h excitedi'r"Moreover; theictimepieceprovidedkbythis inven tuningfcrkf'withthetrotor-"plate; agcornparatively power tionr -operateih-stably againstiiany 'external shock, isi 'p'o t Fiirther," according; to presentinvention, l a s: .ith e re;1 iswused a: tuning forki: whosefi: Q?andiftequency are; much:

higher than of anyi conventifinal' b'alance' lwheel loscillatori andt'ibalance reed; the oscillation energyqkept" hyythha l tuningafork'atthevtime:ofthekoperatiomwill bewell" lat-gens tham thejgloadwner'gyandzclofss energy" Thereforq therecan-11 oscillaton'i'sused.

Fimher; themost'preferahl: embodimentof'the ptesentc. invention lS'ShOWIIY. i'ni 21.. According: to. it; t as:

piecewvhich operatesfistably and. isshigh iaccunacy.

Im the above dcscriptiom. there; has been: chiefly ex plaine :a: casewherein the escape:- wheeliis rotated"'ande'ishiescapc-w it to? the:tuninggfork can.

v arr: OFthe cOnVentionaI-R .halancet'irccdi the" efli'ciency- Willi behigher: andr therefore k obtained a timepiece whose: accuracy is much 1higher-- than:- ofi a timepiece inswhichzthe conventionalt I tion.)

Further, in FIGURES 4 and 5 as the magnet is held be-' 5 magneticallycombined with the magnet secured to the forked end of the tuning fork.(This is called a normal drive in this invention.) On the contrarydthetuning fork can be oscillated at a fixed frequency, the magnet securedto the forked end of the tuning fork and the escape wheel can bemagnetically combined with each other and the escape wheel can berotated at a fixed rotats Sp e tween the escape wheel, both normal andreverse drives can be used by oscillating the tuning fork.

' As described above, the present invention has ad-' vantages in thatthe defects of the conventional magnetic escapement can be completelyeliminated, that the escape wheel can be synchronized with the stableoscillatory motion of the tuning fork and that magnetic escapement veryhigh in precision can be obtained with a simple mechanism.

What is claimed is:

1.,-A magnetic escapement mechanism comprising the combination of a pairof concentric, rotatable escape,

wheels spaced apart from each other and made of a mag- .netic fluxconducting material, a rigid mounting member,

(This is called a reverse drive in this inven-' having a base portionrigidly secured to said mounting member and a pair of tihes projectingfrom said base portion, a pair of magnets each of which is mounted onone of said tines, and a rotatable escape wheel made of a magnetic fluxconducting material shaped to form a plurality of radially extending,circumferentially spaced magnetic teeth, said escape wheel being mountedso that 2. A magneticescapement mechanism as defined in a claim 1wherein the tines of the tuning fork are magneticallycoupled to theescape'wheels by means of a magnet centrally mounted between the escapewheels and between the tines of the tuning fork.

3. A magnetic escapement mechanism comprising the combination ofa rigidmounting member, a tuning fork having, a base portionrigidly secured tosaid mounting member and a pair'of tines projecting from said baseportion, a-pair of magnets each'of which is mounted on one of saidtines, and a rotatable escape wheel made of a magnetic flux-conductingmaterial shaped to provide an undulating magnetic track extending aroundsaid escape wheel,said escape wheel being disposed between said magnetsfor magnetically coupling the tuning fork to the escape wheel at twospaced points whereby the rotation of said escape wheel is synchronizedwith the oscillation-of the tuning fork.

4. A magnetic escapement mechanism comprising the combination of arigid'mounting member, a tuning fork having a base portion rigidlysecured to said mounting member and a pair of tines projecting from saidbase portion, a pair of magnets each of which is mounted on one of saidtines, and a rotatable escape wheel made of a magnetic .flux conductingmaterial and disposed between said magnets for magnetically coupling thetuning fork to the escape wheel at two spaced points, said escape wheelbeing adapted to modify the reluctance between the poles of each of saidmagnets in accordance with the predetermined frequency of said tuningfork whereby the rotation of said escape wheel is synchronized with theoscillation of the tuning fork.

said magnetic teeth pass between the magnetic poles of both of saidmagnets so as to magnetically couple said tuning fork to the escapewheel at two spaced points whereby the rotation of said escape wheel issynchronized with the oscillation of the tuning fork.

6. A magnetic escapement mechanism comprising the combination of a rigidmounting member, a tuning fork having a base portion rigidly secured tosaid mounting member and having a permanent magnet at each of the forkedends, a rotatable escape wheel made of a-magnetic flux conductingmaterial. and having an undulating magnetic track disposed between themagnetic poles of both of said permanent magnets so as to magneticallycouple the tuning fork and the escape wheel at two circumferentiallyspaced points on saidundulating magnetic track whereby the rotation ofthe escape wheel is synchronized with the oscillation of the tuningfork.

7. A magnetic escapement mechanism comprising the combination of arotatable escape wheel made of a mag s netic flux conducting materialand shaped to provide an undulating magnetictrack extending around saidescape wheel, a rigid mounting member, and a tuning'fork hav-.

.ing a base portion rigidly secured to said mounting memher and a pairof titles each having polar formations adapted to follow the magnetictrack on saidescape wheel at two circumferentially spaced points wherebythe speed of rotation of the escape wheel is controlled by the frequency of oscillation of the tuning fork and said polar formationsthereon.

nent magnet mounted on one of said tines and forming a pair of opposedmagnetic 'poles of opposite polarity and 5. A magnetic escapementmechanism comprising the defining an open slot extending in thedirection of oscillatory movement of the tines, said tuning fork havinga weight equivalent to said magnet in moment of inertia attached to theother of said tines, and a rotatable escape wheel made of a magneticflux conducting material and disposed within said slot for magneticallycoupling the tuning fork to the escape wheel, said escape wheel beingadapted to modify the reluctance between said opposed magnetic poles inaccordance with the predetermined frequency of said tuning fork wherebythe rotation of said escape wheel is synchronized with the oscillationof the tuning fork.

References Cited by the Examiner UNITED STATES PATENTS BROUGHTON G.DURHAM, Primary Examiner,

1. A MAGNETIC ESCAPEMENT MECHANISM COMPRISING THE COMBINATION OF A PAIROF CONCENTRIC, ROTATABLE ESCAPE WHEELS SPACED APART FROM EACH OTHER ANDMADE OF A MAGNETIC FLUX CONDUCTING MATERIAL, A RIGID MOUNTING MEMBER ATUNING FORK HAVING A BASE PORTION RIGIDLY SECURED TO SAID MOUNTINGMEMBER AND A PAIR OF TINES PROJECTING FROM SAID BASE PORTION INTO THESPACE BETWEEN SAID ESCAPE WHEELS,